1. Field of the Invention
The present invention relates to a liquid ejection head for ejecting a liquid in the form of droplets through ejection orifices, a recording device board for use in the liquid ejection head, and a manufacturing method for the same.
2. Description of the Related Art
A typical recording device board for use in a liquid ejection head for ejecting a liquid is constructed as shown in FIGS. 15A to 15C. Also, as shown in FIG. 16, the recording device board is electrically connected to a flexible film wiring board.
More specifically, as shown in FIGS. 15A to 15C, a recording device board J1100 for use in the liquid ejection head has an ink supply port J1102 formed to penetrate through it for supplying ink from the rear side. On the surface of a Si substrate J1110, a plurality of electro-thermal transducers (not shown) for applying ejection energy to the ink are arranged on each of both sides of the ink supply port J1102. An ejection substrate J1109 is disposed on the Si substrate J1110, and a plurality of ejection orifices J1107 are formed through the ejection substrate J1109 in one-to-one opposite relation to the plurality of electro-thermal transducers. Further, in both end portions of the surface of the Si substrate J1110, a plurality of electrode pads J1104 are provided and electrically connected to the corresponding electro-thermal transducers.
As shown in FIG. 16, a recording device unit J1002 is constructed such that the plurality of electrode pads J1104 provided on the Si substrate J1110, stud bumps J1105 electrically joined to respective surfaces of the corresponding electrode pads J1104, and a plurality of electrode leads J1013 provided on a flexible film wiring board J1300 are electrically interconnected by, e.g., single point bonding.
A first sealing-resin material J1307 is filled around the Si substrate J1110. Electrically connected portions on the Si substrate J1110 are entirely covered with a second sealing resin material J1308 to protect those connected portions against corrosion caused by ink and disconnection caused by external forces. The first and second sealing resin materials J1307, J1308 are each made of an ordinary thermosetting resin and ensure firm rigidity after setting.
However, the known method of manufacturing the ink jet recording head, described above, has the following problems to be overcome.
In the known method of manufacturing the ink jet recording head, the stud bumps joined to the surfaces of the electrode pads on the recording device board and the electrode leads provided on the flexible film wiring board are electrically connected to each other in a heated state at about 200° C. by using a heat tool, which is heated up to about 500° C., with gang bonding for electrically connecting all the connection points at a time or single point bonding for electrically connecting the connection points one by one.
In the known method of manufacturing the ink jet recording head, therefore, a temperature drop of the flexible film wiring board down to the normal temperature after the bonding causes thermal shrinkages of the electrode leads and a base film, whereupon mechanical loads are imposed on the recording device board and joined portions on it, i.e., the electrically connected portions between the stud bumps and the electrode pads. As a result, the stud bumps may be peeled off from the electrode pads on the recording device board, and the recording device board may be damaged.
As a result of conducting studies with the above-mentioned problems in mind, the inventor has found that the joined portions can be reinforced by filling a sealing resin material so as to cover the peripheries of connection surfaces between the stud bumps and the electrode pads. This method, however, has a problem that it is very difficult to adjust the filling amount of the sealing resin material. If the filling amount is too small, the joined portions cannot be fully covered in a satisfactory condition. Conversely, if the filling amount is too large, the stud bumps are completely covered and the electrical connection cannot be ensured.